Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
  • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
  • F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
  • F01N3/08—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous
  • F01N3/10—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust
  • F01N3/24—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust characterised by constructional aspects of converting apparatus
  • F01N3/28—Construction of catalytic reactors
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
  • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
  • F01N13/00—Exhaust or silencing apparatus characterised by constructional features ; Exhaust or silencing apparatus, or parts thereof, having pertinent characteristics not provided for in, or of interest apart from, groups F01N1/00 - F01N5/00, F01N9/00, F01N11/00
  • F01N13/009—Exhaust or silencing apparatus characterised by constructional features ; Exhaust or silencing apparatus, or parts thereof, having pertinent characteristics not provided for in, or of interest apart from, groups F01N1/00 - F01N5/00, F01N9/00, F01N11/00 having two or more separate purifying devices arranged in series
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
  • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
  • F01N2240/00—Combination or association of two or more different exhaust treating devices, or of at least one such device with an auxiliary device, not covered by indexing codes F01N2230/00 or F01N2250/00, one of the devices being
  • F01N2240/20—Combination or association of two or more different exhaust treating devices, or of at least one such device with an auxiliary device, not covered by indexing codes F01N2230/00 or F01N2250/00, one of the devices being a flow director or deflector
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
  • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
  • F01N2330/00—Structure of catalyst support or particle filter
  • F01N2330/02—Metallic plates or honeycombs, e.g. superposed or rolled-up corrugated or otherwise deformed sheet metal
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
  • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
  • F01N2330/00—Structure of catalyst support or particle filter
  • F01N2330/06—Ceramic, e.g. monoliths
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
  • Y02A50/00—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE in human health protection, e.g. against extreme weather
  • Y02A50/20—Air quality improvement or preservation, e.g. vehicle emission control or emission reduction by using catalytic converters

Definitions

• the present invention relates to a catalytic exhaust gas purification arrangement according to the preamble of appended claim 1.
• Catalytic exhaust gas purifiers are often used in connection with motor vehicles in order to purify the exhaust gases from the vehicle's engine.
• present catalytic converters catalysers
• catalysers are not able to operate at full purification efficiency in connection with cold- starting of a vehicle.
• This problem can be overcome by arranging an additional, electrically-heatable start catalyser in front of the ordinary catalyser. By heating up the start catalyser electrically, the warm-up time for the ordinary catalyser can be shortened, which results in improved purification efficiency during cold starts.
• Such a catalyser arrangement is known from the patent document WO 89/10470.
• a problem which occurs in connection with an electrically- heatable start catalyser is that it requires a powerful electrical supply in order to be activated. This can for example be achieved by arranging an additional battery in the vehicle, which is however unnecessarily expensive and complicated. It is therefore desirable to have a catalyser arrangement which is not dependent on an electrical supply, but which still produces a shortening of the main catalyser ' s "ignition" time (the so-called "light-off” time), i.e. the time which elapses from starting the engine until the catalyser is working at optimal purification efficiency. This should, in such a case, result in improved purification efficiency of the entire catalyser arrangement.
• a main object of the present invention is to solve the aforementioned problems and provide an improved arrangement for catalytic exhaust gas purification, in particular for shortening the light-off time of such an arrangement. This is achieved with an arrangement of the type mentioned in the introduction, the characterising features of which are defined in appended claim 1.
• An additional object of the invention is to achieve a correct measurement of the conversion efficiency of the aforementioned catalyser arrangement, in order to provide information for a diagnosis of its operation. This allows an indication, e.g. in the form of a warning light, which warns the vehicle driver that the catalyser is defective and has to be replaced.
• Fig. 1 is a side view of an arrangement according to a preferred embodiment of the present invention
• Fig. 2 is a view from above of the arrangement according to Fig. 1,
• Fig. 3 is a cross-sectional view along line
• Fig. 4 is an enlarged partial view which shows a portion of the arrangement according to Fig. 1,
• Fig. 5 is a side view of an alternative embodiment of the invention.
• Fig. 6 is a side view of an arrangement which is similar to that in Fig. 1, but which has been provided with lambda sensors for diagnosing the operation of the catalyser arrangement,
• Fig. 7 is a somewhat enlarged view, seen from above, of a further embodiment of the invention.
• Fig. 8 is a cross-sectional view along the line B-B in Fig. 7. Description of preferred embodiments:
• Fig. 1 shows a side view of an arrangement in accordance with the present invention.
• the arrangement comprises a catalytic exhaust gas purifier with a first monolithic catalyser unit 1. Downstream of the first catalyser 1 there is a main catalyser which is constituted by a second monolithic catalyser 2 and a third monolithic catalyser 3.
• the first catalyser 1 is preferably constituted by a metallic catalyser which has a circular cross-section with about 98 mm diameter and a length of between 74 and 90 mm, as well as a cell density of the order of 200 cpsi (cells per square inch) .
• a metallic catalyser has the advantage that it has a considerably larger catalytic active area than a ceramic catalyser. Another advantage is that the energy is transported quickly from this to the second catalyser 2.
• the second catalyser 2 and the third catalyser 3 are preferably constituted by similar ceramic catalysers of the monolithic, three-way catalyser type. Other types of catalysers are also possible.
• the two catalysers 2, 3 are formed so that their size and cell-density are substantially the same, whilst other parameters such as length and type of catalytic coating can be different.
• An inlet channel 4 is arranged upstream of the first catalyser 1.
• the exhaust gases flow through the inlet channel 4 from a combustion engine of conventional type (not shown) .
• the part of the inlet channel 4 which lies closest to the first catalyser 1 is somewhat widened, which gives an optimal flow of the exhaust gases through the inlet channel 4.
• the inlet channel 4 presents an angle with respect to the longitudinal direction of the catalysers 1, 2, 3, which lies between 10° - 40°, preferably about 20°.
• the complete arrangement is enclosed in a common casing 5 of metal .
• the arrangement also includes an outlet channel 6, through which the exhaust gases flow when they have passed through all of the catalysers 1, 2, 3.
• the outlet channel 6 is preferably formed as a straight, relatively long conical section. This arrangement is advantageous with respect to the flow characteristics of the exhaust gases at the outlet of the catalyser arrangement.
• Fig. 2 shows a view from above of the arrangement according to the invention. From this figure, as well as from figure 3 which is a cross-sectional view along the section A-A in figure 2, it is clear that the second catalyser 2 and the third catalyser 3 have a substantially oval cross-section.
• the first catalyser 1 has a considerably smaller cross-sectional area than the second and third catalysers 2, 3.
• the ratio between the size of the cross- sectional area of the first catalyser 1 and the second catalyser 2 is between 0.5:3 - 2.9:3, preferably 2:3.
• the first catalyser 1 also has a relatively small volume. This means that it is heated up relatively quickly due to the heat from the exhaust gases and the heat from the catalytic reaction in the catalyser 1. Thus a catalytic reaction will be started up quickly in the first catalyser 1.
• the second catalyser 2 is a ceramic catalyser which has a lower thermal conductivity than the first catalyser 1 which is a metallic catalyser. This contributes to an efficient operation of the entire catalyser arrangement.
• the inlet channel 4 is angled with respect to the longitudinal axis of symmetry of the first catalyser 1. This means that the cross-sectional area through the inlet channel 4 is less than the cross- sectional area for the frontal surface of the first catalyser 1, onto which the exhaust gases are incident. In this way, a turbulent flow in front of the first catalyser 1 is avoided and instead a laminar flow of the exhaust gases through the inlet channel 4 is obtained up until they reach the first catalyser 1.
• the first catalyser 1 is, in a known manner, formed with a number of longitudinal channels, of which three channels 7, 8, 9, are shown in figure 4.
• the channels 7, 8, 9 are substantially straight, i.e. they follow the longitudinal direction of the catalyser 1, but they can also have another form, e.g. a curved shape or a zig-zag shape.
• the exhaust gas flow is shown schematically with arrows 10, 11, and 12 respectively.
• the exhaust gas stream/flow has a laminar flow through the inlet channel 4.
• the laminar flow effectively goes through a transition to a turbulent flow.
• This is indicated in figure 4 with "turbulent" flow lines 13, 14 and 15.
• the transition from laminar to turbulent flow occurs as a result of the inlet channel 4 being angled, both in the height direction and the sideways direction, with respect to the longitudinal direction of the first catalyser 1.
• the turbulent flow gives rise to a rapid heating of the first catalyser 1, due to which its catalytic reaction can start quickly.
• the turbulent flow again goes through a transition to a laminar flow.
• Fig. 5 shows a side view of an alternative embodiment of the invention.
• it comprises a comparatively small first catalyser 1 and a main catalyser comprising a second catalyser 2 and a third catalyser 3.
• it comprises an inlet channel 4 which is slanted with respect to the first catalyser 1.
• This alternative embodiment also comprises a casing 5 with an intermediate portion 16 which is arranged between the first catalyser 1 and the second catalyser 2.
• the first catalyser 1 is somewhat slanted with respect to the intermediate portion 16, i.e.
• the longitudinal axis of symmetry of the first catalyser 1 forms an angle to the longitudinal axis of symmetry of the intermediate portion 16.
• the intermediate portion 16 is formed so that its longitudinal axis of symmetry forms an angle to the longitudinal axis of symmetry of the second catalyser 2. In this way, a zone with turbulent flow is also formed at the inlet to the second catalyser 2. This assists in giving an increased efficiency of the entire catalyser arrangement by the second catalyser 2 having a shorter light-off time.
• Figure 6 is a side view of a further embodiment of the invention which is similar to that shown in Fig. 1 but which further comprises two lambda sensors 17, 18 which can be used for measuring the degree of conversion of the catalyser arrangement.
• a lambda sensor is a type of sensor which produces an electrical signal which varies with the oxygen content of the exhaust gases.
• a first lambda sensor 17 is arranged in front of the first catalyser 1 and a second lambda sensor is arranged after the third catalyser 3.
• Both of the lambda sensors 17, 18 are also connected to an analyzer unit (not shown) which, on the basis of the signals from the lambda sensors 17, 18, can calculate a value of the degree of conversion of the catalyser arrangement, i.e. its purification ability.
• an alarm signal can be activated.
• Such a signal can be constituted by e.g. a warning light on the motor vehicle ' s instrument panel. The driver of the vehicle can thus be made aware that the catalyser arrangement needs to be replaced.
• a special problem can arise if the catalytic active coating of the catalysers has a high oxygen storage capacity, which can sometimes be the case with modern catalysers. This leads to the following problem arising during a diagnosis with the aid of the lambda sensors 17, 18. If the second lambda sensor 18 is placed in the outlet channel 6 (see figure 6), and the catalysers 1, 2, 3 arranged upstream have a high oxygen storage capacity, only a small amount of oxygen will be available at the second lambda sensor 18. This means that the signal from the second lambda sensor 18 becomes unstable and can vary greatly. In the worst case, the signal can be interpreted by the analyzer unit as being a signal indicating a malfunctioning catalyser.
• the second lambda sensor 18 can be arranged in another place than after the third catalyser 3, e.g. between the first catalyser 1 and the second catalyser 2 or between the second catalyser 2 and the third catalyser 3. In this way, reliable measurements can be obtained.
• the second lambda sensor 18 in the case that it is wished to place the second lambda sensor 18 as close as possible downstream of the first catalyser 1, problems can arise concerning the space which is available in the vehicle.
• the first catalyser 1 can be arranged somewhat displaced in the sideways direction, i.e. with respect to the symmetrical longitudinal axis of the second catalyser 2. This arrangement is shown in figure 7.
• Figure 8 which shows a cross-section along line B-B in figure 7, defines a possible placement of the first catalyser 1 with respect to the second catalyser 2.
• the main catalyser can be constituted by a single catalyser instead of the two above-mentioned catalysers 2 and 3.
• the first catalyser 1 can be combined with a so-called HC-trap or an electrically heatable catalyser, e.g. an electrical start-catalyser or a gas burner. In this way, an additional improvement of the purification efficiency can be achieved.

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• Engineering & Computer Science (AREA)
• Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Combustion & Propulsion (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Health & Medical Sciences (AREA)
• Toxicology (AREA)
• Exhaust Gas After Treatment (AREA)
• Exhaust Gas Treatment By Means Of Catalyst (AREA)

Priority Applications (4)

Applications Claiming Priority (2)

Publications (1)

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Cited By (5)

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Citations (4)

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• 1995
  • 1995-03-01 SE SE9500748A patent/SE504095C2/sv not_active IP Right Cessation
• 1996
  • 1996-02-27 WO PCT/SE1996/000247 patent/WO1996027078A1/en not_active Application Discontinuation
  • 1996-02-27 DE DE69613355T patent/DE69613355T2/de not_active Revoked
  • 1996-02-27 JP JP52619496A patent/JP3654651B2/ja not_active Expired - Fee Related
  • 1996-02-27 EP EP96905098A patent/EP0812382B1/en not_active Revoked
  • 1996-02-27 US US08/913,346 patent/US5996339A/en not_active Expired - Fee Related

Patent Citations (4)

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